Public health concerns surrounding the cVDPV2 outbreak in Africa: Strategies for prevention and control with a special focus on Nigeria

Abstract Background and Aim Poliovirus is a global health issue that affects children in different parts of the world. Despite the efforts of national, international, and nongovernmental organizations to eradicate the disease, it is re‐emerging in Africa due to poor sanitation, vaccine hesitancy, new ways of transmission, and poor surveillance among others. Circulating vaccine‐derived poliovirus type 2 (cVDPV2) is a major step in eradicating poliovirus and preventing outbreaks in developing countries. Strengthening African healthcare systems, increasing surveillance, hygiene and sanitation, and proper mass vaccination to achieve herd immunity are required in the fight against polio disease. This paper discusses the outbreak of cVDPV2, public health challenges, and recommendations in Africa with a special emphasis on Nigeria. Methods We searched for articles documenting the incidence of cVDPV2 in Nigeria and other African countries on Pubmed, Google Scholar, and Scopus. Results A total of 68 distinct cVDPV2 genetic emergences were found across 34 nations between April 2016 to December 2020, and in Nigeria, three cVDPV2 emergences were found. Also, 1596 instances of acute flaccid paralysis linked to cVDPV2 outbreaks were reported in four areas of the World Health Organization where Africa contributed 962 cases out of 1596 cases. Available data indicate that Africa has the most cVDPV2 cases and is associated with various challenges like the unidentified virus source, poor sanitation system, and inability to achieve herd immunity of the cVDPV2 vaccine. Conclusion Collaborative efforts of stakeholders are crucial in combating infectious diseases, especially those transmitted via environments such as water and air, like poliovirus. Therefore, a collaboration between environmental health workers, veterinarians, community health workers, laboratory scientists, policymakers, and other professionals is required.


| INTRODUCTION
Despite the tremendous effort by governments, the World Health Organization (WHO), United Nations International Children's Emergency Funds (UNICEF), Global Polio Eradication Initiative (GPEI) in the prevention of circulating vaccine-derived poliovirus type 2 (cVDPV2) globally, outbreaks of these viruses have been occurring in a different part of the world. This is more evident in African countries that have indigent healthcare delivery services with poor sanitation and hygiene. 1 cVDPV2 outbreaks is a great burden to GPEI because it is challenging to convince health professionals and the affected communities that administering the same vaccine with high coverage is the best method for controlling outbreaks and preventing re-emergences. 2 Between April and July 2022, a cVDPV2 with acute paralysis was identified in Algeria, Africa. The case was reported to World Health Organization by the Global Polio Laboratory Network. The issue was identified in a toddler, under two, from the Southern Algerian region of Tamanrasset who was diagnosed with acute flaccid paralysis.
However, this is the first case ever found in the country. Following laboratory diagnosis of a fecal sample, the Pasteur Institute of Algeria and the Pasteur Institute of Paris revealed circulating vaccine-derived poliovirus 2 in the sample. According to genomic sequencing analysis, the newly discovered virus was genetically related to the one previously discovered in Kano, Nigeria. However, the child had not gotten any doses of the polio vaccine and had never traveled outside the province of Tamanrasset. 3 There is no evidence or information on how the child contracted the virus; calling for further studies focusing more on studying the mechanism of the virus transmission. 4 Kano state is a metropolis in northern Nigeria with more than four million residing within a 449-km square area; it is the second largest state in Nigeria after Lagos. Situated in the savannah, south of the Sahel, Kano state has attracted a large number of foreigners from different parts of the world, especially people from Asia and Africa, as it is a key trans-Saharan trade route. 5 This paper discusses the outbreak of cVDPV2, public health challenges, and recommendations in Africa with a special emphasis on Nigeria.

| POLIOMYELITIS
Poliomyelitis is a viral infection caused by a virus belonging to the picornaviridae family. It is a very contagious infection with a milder episode of respiratory sickness, gastroenteritis, and malaise to severe types of paralysis. This has been categorized into in-apparent infection, abortive poliomyelitis, nonparalytic poliomyelitis, and paralytic poliomyelitis is the disease's hallmarks. 6 Poliovirus had a cosmopolitan distribution before the introduction of mass immunization campaigns, which may be due to poor environmental hygiene in low and middle countries. The highest incidence of the disease occurs in industrialized and temperate countries. 7 Person-to-person contact is the main route of transmission of the virus. Following infection, the virus enters through the mouth and invades the intestine, which is subsequently expelled into the environment through the feces (feacal-oral route of transmission). 2 This virus further spread into the environment, particularly under poor hygiene and sanitation conditions. 2 However, when a considerable number of children are protected against the virus, its infection rate will reduce because it cannot infect any more children who are susceptible or vulnerable to infection. 8 Environmental surveillance is used to detect poliovirus circulation, especially in environmental sewage, and to track transmission in communities as part of the WHO's global action plan for eradicating poliomyelitis. Environmental surveillance supplements clinical acute flaccid paralysis surveillance for potential polio cases. 9 It has been discovered that asymptomatic people shed significant amounts of the virus into the sewerage system. 10 In developing countries, particularly Nigeria, in areas where water is scarce, farmers use water from sewages to water their plants-mostly vegetables and fruits-which are sold to people for consumption, making them susceptible to infections.  In compliance with the updated international polio outbreak response standard operating procedures, 12 a response was activated. So also, a reactive vaccination effort was considered.

| Nigeria
Interestingly, Nigeria continues to experience the transmission of vaccine-derived poliovirus (cVDPV2) in spite of the wild poliovirus being declared eradicated in August 2020. 13  Somalia, declared the outbreak as a regional public health emergency and took part in the regional outbreak response since the cVDPVs was discovered in the Horn of Africa in 2018. Somalia is at a high risk of further spreading this isolated cVDPV2 due to their population's movements across borders in the horn of Africa, the subnational immunity, and surveillance gaps. Normally, the GPEI partners support when needed as the Ministry of Health and local health authorities conduct thorough investigations. Active surveillance was intensified, subnational population immunity levels were analyzed, and an epidemic response was developed; coupled with epidemiological and virological field study.

| One health approach
One health is a collaborative, multisectoral, and transdisciplinary approach that operates at the local, regional, national, and global levels to achieve the best possible health outcomes by comprehending the links between people, animals, plants, and their environments. 16 The need for utilizing this approach to the control of polio disease is important for achieving a polio-free community in Africa.
The system's efficiency will rise because of this integration, which will quicken decision-making procedures and enhance coordination.

| CONCLUSION
The Polio outbreak is re-emerging despite the efforts of various actors including WHO, NGOs, governments, and health authorities.
Poor sanitation, vaccine hesitancy, new ways of transmission, and poor surveillance are some of the contributory factors to the reemergence of the disease. To prevent the re-emergence of the disease, surveillance should be intensified, efforts should be made toward vaccine equity, international travelers should be properly monitored, public involvement should be increased, One Health Approach should be adopted, and high-income countries should continue to support Africa. A collaboration between environmental health workers, veterinarians, community health workers, laboratory scientists, policymakers, and other professionals at the national, regional, and district levels is crucial in fighting and preventing the reemergence of the disease, and for that matter polio-free Africa.

CONFLICT OF INTEREST STATEMENT
The authors declare no conflict of interest.

DATA AVAILABILITY STATEMENT
Not applicable.

TRANSPARENCY STATEMENT
The lead author Ridwan O. Adesola affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.